C++ Fuzzy Logic loop increments after first input

Question

I wrote my first Fuzzy Logic program and the first input does its job perfectly by outputting the correct voltage value. The word Voltage is strictly a place holder. It matches my math exactly. Any value afterwards, increases the final output and NEVER works again until I reset the program, upon which, it does the same thing.

I'll try to simplify my code as much as possible.

int main()
{
int InputDistance;
double BetweenDistance1;
double BetweenDistance2;
double DoM1;
double DoM2;
double OutputComponent1;
double OutputComponent2;
double CrispOutput;
bool NN = false;
bool N = false;
bool Z = false;
const double NNVolt (0);
const double NVolt (2.25);
const double ZVolt (4.5);
for(;;)
{
        cout <<  "What is the distance?" << endl << endl;
        cin >> InputDistance;
        cout << endl;
        if(InputDistance > 0 && InputDistance <= 5)
        {
            BetweenDistance1 = InputDistance - 0;
            BetweenDistance2 = 5 - InputDistance;
            NN = true;
            N = true;
        }
        if(InputDistance > 5 && InputDistance <= 10)
        {
            BetweenDistance1 = InputDistance - 5;
            BetweenDistance2 = 10 - InputDistance;
            NN = true;
            N = true;
        }
        if(InputDistance > 10 && InputDistance <= 15)
        {
            BetweenDistance1 = InputDistance - 10;
            BetweenDistance2 = 15 - InputDistance;
            N = true;
            Z = true;
        }
        if(InputDistance > 15 && InputDistance <= 20)
        {
            BetweenDistance1 = InputDistance - 15;
            BetweenDistance2 = 20 - InputDistance;
            N = true;
            Z = true;
        }

        DoM1 = BetweenDistance1 / 5;
        DoM2 = BetweenDistance2 / 5;

        if(NN == true && N == true)
        {
            OutputComponent1 = NNVolt * DoM1;
            OutputComponent2 = NVolt * DoM2;
        }
        if(N == true && Z == true)
        {
            OutputComponent1 = NVolt * DoM1;
            OutputComponent2 = ZVolt * DoM2;
        }
        CrispOutput = OutputComponent1 + OutputComponent2;

        cout << "Voltage = " << CrispOutput << endl << endl;
    }
    return (0);
}

What is causing the values to increment every time I input a new distance value? I can't see it.

Answer 1

You are never resetting your bool s.

bool NN = false;
bool N = false;
bool Z = false;

Should be at that start of your for loop so that they are reset every time it loops.

As a rule of thumb any variable that you will use in a loop should be declared in the loop unless you need to access it outside the scope of the loop.

Answer 2

You should initialize all your variables, because even though your compiler will initialize them to null, "", preppended "\\0", 0, 0.0, 0.0f it's can be taken to be compiled under a different compiler that doesn't follow such a standard, or compiling with flags that initialize using different stuff.

int main()
{
    int InputDistance = 0;
    double BetweenDistance1 = 0.0;
    double BetweenDistance2 = 0.0;
    double DoM1 = 0.0;
    double DoM2 = 0.0;
    double OutputComponent1 = 0.0;
    double OutputComponent2 = 0.0;
    double CrispOutput = 0.0;
    bool NN = false;
    bool N = false;
    bool Z = false;
    const double NNVolt (0);
    const double NVolt (2.25);
    const double ZVolt (4.5);

And you should re-initialize at the beginning of the loop to make sure you don't end up using data from previous iterations.

    for(;;)
    {
            //----------- init ------------
            InputDistance = 0;
            BetweenDistance1 = 0.0;
            BetweenDistance2 = 0.0;
            DoM1 = 0.0;
            DoM2 = 0.0;
            OutputComponent1 = 0.0;
            OutputComponent2 = 0.0;
            CrispOutput = 0.0;
            NN = false;
            N = false;
            Z = false;
            //-----------------------------

            cout <<  "What is the distance?" << endl << endl;
            cin >> InputDistance;
            cout << endl;

            ..            

        }

        return (0);
}